Recently, so-called cable televisions are spreading widely as multi-channel media in areas other than remote areas and blind spots. FIG. 1 shows an example of a cable television receiver. A data receiving section 1 extracts a receiver control signal from a cable television signal transmitted from a cable television station, and supplies it to a host processor 2. The host processor 2 controls the entire receiver, based on a control signal and a tuning operation by an audience. A receiving tuner 3 extracts the signal of a program selected by the tuning operation of the audience from the cable television signal, and outputs it to a descrambler 4. The descrambler 4 uses a synchronization signal supplied from an AM wave detecting circuit 7, to release the scramble of the program signal, and outputs this signal to a video wave detecting circuit 5 and the AM wave detecting circuit 7. The video wave detecting circuit 5 extracts a video signal from the program signal and demodulates it. Further the circuit 5 outputs the other components of the program signal to a FM wave detecting circuit 6. The FM wave detecting circuit 6 demodulates an audio signal.
As described above, in case of the cable television, information (video signal, audio signal, and control signal) is transmitted as an analogue signal. Therefore, processing for compressing and multi-layering information cannot be performed. Consequently, the number of channels (programs) that can be provided by a cable television is limited to about 60.
At present, in the digital multi-channel satellite broadcasting (e.g., PerfecTV (trademark)) which is spreading widely, 100 or more channels have been realized. The market needs further multiplication of channels in the cable television.
To realize further multiplication of channels in the cable television, the following way may be considered. That is, videos can be multi-layered by compression if all signals are digitized in cable television stations. However, this is difficult to realize when considering the costs of equipments and running costs for the cable television stations. Hence, consideration is taken into a method of further multiplying channels in the cable television by redeliver digital multi-channel satellite broadcasting such as PerfecTV.
The digital multi-channel satellite broadcasting system will now be explained with reference to FIG. 2. The transmission section 11 of a satellite service provider 10 performs scrambling on MPEG-compressed program information supplied from a program provider, and multi-layers it together with service information such as electronic program guide information (EPG: Electric Program Guide), audience management information, and the like. The transmission section 11 further transmits them as a CS of a linear polarized wave to a communication satellite 20. This CS wave is transmitted to a receiving terminal apparatus 30 through the communication satellite 20, and is received by a receiver 32 through a CS antenna 31. The receiver 32 extracts predetermined program information from the CS wave and outputs it to a television receiver 33. An audience management section 12 issues an IC card 34 to an audience. A key management section 13 of the audience management section 12 manages audible programs corresponding to the IC card 34. An audience information processing section 14 calculates an audience fee, based on audience information notified by the receiver 32, and notifies a customer management section 15 of it. The customer management section 15 charges the audience fee to the audience.
FIG. 3 shows a specific structure of the receiver 32. A receiving tuner 92 of a satellite front end section 91 extracts a transport stream (TS) including a predetermined program, from a CS wave, and output it to a QPSK demodulation circuit 93. The QPSK demodulation circuit 93 QPSK-demodulates the inputted TS and outputs it to an error correction circuit 94. The error correction circuit 94 corrects error information of the inputted TS and outputs it to a transport section 55. A descrambler 56 of the transport section 55 descrambles the TS which has been scrambled, with use of descrambling information recorded in an IC-card 34 which the satellite broadcasting service provider 10 issued. The descrambler 56 further outputs it to a demultiplexer 57.
The demultiplexer 57 extracts information of a predetermined program, based on multi-layered program specific information (PSI), and provides it to an MPEG decoding section 58. The MPEG decoding section 58 MPEG-expands an inputted program to generate a video signal and an audio signal, and outputs them to a television receiver 33.
A host processor 59 controls the entire receiver 32 in response to an operation by an audience, and records information (program audience information) of a received pay program on the IC card 34. The host processor 59 also reads descramble information recorded on the IC card 34 and supplies it to the descrambler 56. Further, the host processor 59 controls the communication section 61 to notify periodically an audience information processing section 14 of program audience information recorded on the IC card 34. The audience information processing section 14 calculates an audience fee, based on the inputted audience information, and notifies the customer management section 15 of it.
To provide digital multi-channel satellite broadcasting signals to the cable television network, however, the cable television station needs processing, e.g., receiving a digital multi-channel satellite broadcasting signal, separating a multi-layered signal, and multi-layering again the signal. The equipments thereof require enormous costs.
To provided digital multi-channel services in a plurality of cable networks, each cable network needs an apparatus for digitizing a plurality of programs, and an equipment for managing customers, which require enormous equipment investment and management costs.
Further, the method for providing services, such as CS digital services, BS digital services, and ground digital services, differs depending on media. Therefore, transmission, methods must be unified between the cable networks each other, to receive them by one common receiver.
In addition, in a method of reconstructing and transmitting a service from a satellite in a cable network, it is impossible to receive services such as EPG services and download services, which are unique to digital services.
Further, in provided digital multi-channel satellite broadcasting, it is difficult for cable television stations to carry out audience information management, if specific charge such as pay-per-view is taken.
In case where a digital multi-channel satellite broadcasting signal is transmitted again to a cable station or a public institution in a modulation conversion method, frequency information and program information at least in network information must be converted into information which matches with contents of retransmission in the cable station or public institution, because of necessity for receiving operations by a receiver.
If retransmission is achieved by only modulation conversion without converting network information, a special function is required, e.g., it is necessary to include a correspondence table by which the frequency information physically transmitted in a receiving system and the frequency information contained in the network information are related to each other.
If a program information part in the network information is not changed, all programs that are served by a satellite system must be re-transmitted to cables.
Also, in case of a transport stream which does not have network information matched with the service in the network as a retransmission target, operation errors may be caused or audience may be confused when the stream is received by in a receiver.
Further, if original network information is not used but network information matched with the network as a retransmission target is generated in a unique manner and rewriting is carried out, it is difficult to match the data length of the network information with the original data length, so the structure of the apparatus is complicated.